Energy saving, environment protection and safety become the development directions of the mechanical manufacture industry with the aggravation of worldwide energy crisis and environment problem, thus it is required to improve the utilization of the steel resource and reduce the consumption of the steel resource during the machinery manufacturing process.
A cold stamping process is generally employed for manufacturing various mechanical parts, wherein, a steel plate as a blank is pressed into a gap of a mold for manufacturing a mechanical part under the normal temperature, thus the steel plate is shaped in the mold to make the mechanical part. Generally, most of the mechanical parts, such as bracket parts as an electrical machine bracket, and disc parts, have multiple bent portions, and the bent portions are generally treated to rounded corners. However, the steel plate has a small ductility under the normal temperature, in this case, during the process of manufacturing the mechanical parts with the existing cold stamping process, the steel plate is hard to pass through the rounded corner since the steel plate is hard to bend when being stamped to the rounded corner in the gap of the mold, thus the one-step forming, i.e., directly forming the whole part by pressing one piece of steel plate into the entire gap of the mold, can not be realized by using the cold stamping process. Thus, in the process for manufacturing the mechanical part by cold stamping, a manner of multiple-steps forming and welding is generally employed, that is, portions, without a rounded corner, of the part are formed by stamping separately, and then these portions are welded together to form the whole part. Reference is made to FIG. 1, which shows an electrical machine bracket manufactured by cold stamping and welding. During the welding process, portions of the part to be welded together are required to have overlapped portions therebetween, thus when the mechanical parts is manufactured in the manner of multiple-steps forming and welding using the cold stamping, more steel plate materials may be consumed.
At present, in order to avoid the problem of high consumption of steel plate materials caused by using the cold stamping process, a hot stamping process may be employed to manufacture the mechanical parts. In the hot stamping process, a steel plate as a blank is heated, and the heated steel plate is pressed into the mold of the part when the steel plate is at a high temperature, thereby forming the mechanical part. The steel plate at a high temperature has a good ductility, thus during the stamping process, the steel plate is apt to be deformed to pass through the gap at the rounded corner, thus the one-step forming, i.e., directly forming the whole part by pressing one piece of steel plate into the mold, can be realized by using the hot stamping, thereby reducing the consumption of the steel resources during the manufacturing process of the mechanical parts. However, during the hot stamping process, when being passed through the gap at the rounded corner of the mold, the steel plate may subject to a resistance force to generate wrinkles, and wrinkles continually generated in the stamping process may be irregularly accumulated, and if the stamping process continues, the steel plate is apt to be cracked at the wrinkles. Thus, cracked parts are apt to be generated by using the hot stamping process to manufacture the mechanical parts, and the cracked parts are useless, which increases a rejection rate, and not only increases the production cost, but also causes a waste of the steel resources.